A Precision, Energy-Efficient, Oversampling, Noise-Shaping Differential SAR Capacitance-to-Digital Converter

Type
Article

Authors
Alhoshany, Abdulaziz
Salama, Khaled N.

KAUST Department
Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division
Electrical Engineering Program

Online Publication Date
2018-06-25

Print Publication Date
2019-02

Date
2018-06-25

Abstract
This paper introduces an oversampling, noise-shaping differential successive-approximation-register capacitance-to-digital converter (CDC) architecture for inter-facing capacitive sensors. The proposed energy-efficient CDC achieves high-precision capacitive resolution by employing oversampling and noise shaping. The switched-capacitor (SC) integrator is inserted between the comparator and the charge-redistribution digital-to-analog converter to implement noise shaping and to make the interface circuit insensitive to parasitic capacitances. An inverter-based operational transconductance amplifier with a common-mode feedback circuit is employed to implement the SC integrator with subthreshold biasing for low voltage and low power. The ring-oscillator-based comparator is implemented to achieve high energy efficiency. The test chip is fabricated in a 0.18-μm CMOS technology. The proposed CDC experimentally achieves 150 aF absolute resolution and 12.74-ENOB with an oversampling ratio of 15 and a sampling clock of 18.51 kHz. The fabricated prototype dissipates 1.2 and 0.39 μW from analog and digital supplies, respectively, with an energy efficiency figure-of-merit of 187 fJ/conversion step.

Citation
Alhoshany A, Salama KN (2018) A Precision, Energy-Efficient, Oversampling, Noise-Shaping Differential SAR Capacitance-to-Digital Converter. IEEE Transactions on Instrumentation and Measurement: 1–10. Available: http://dx.doi.org/10.1109/tim.2018.2844899.

Acknowledgements
This work was supported by the King Abdullah University of Science and Technology. The Associate Editor coordinating the review process was Niclas Bjorsell.

Publisher
Institute of Electrical and Electronics Engineers (IEEE)

Journal
IEEE Transactions on Instrumentation and Measurement

DOI
10.1109/tim.2018.2844899

Additional Links
https://ieeexplore.ieee.org/document/8395284/

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